Vapor recovery systems for fuel dispensing devices have been the subject of previous patents. The subject of monitoring or testing such vapor recovery systems, however, is not as well developed. The following references illustrate the general state-of-the-art pertaining to vapor recovery system testing.
U.S. Pat. No. 5,715,875 to Clary et al. describes a method and apparatus for dry testing vapor recovery systems. The apparatus is essentially a valve having two mechanisms for opening the valve. The first mechanism opens the valve when fuel is being dispensed while the second valve selectively opens the valve without regard to whether the system is dispensing fuel. The focus of Clary et al. is on the physical structure of the valve which allows for "dry testing" of the vapor recovery system by simulating the rate of fuel that would be dispensed without actually having to dispense any fuel and comparing vapor recovery path measurements against the simulated rate in order to determine the effectiveness of the vapor recovery system. Clary et al. appears to be limited to testing vapor recovery rates in general and purports to be able to identify when vapor recovery rates are inadequate. However, Clary et al. does not suggest specific reasons for insufficient rates.
U.S. Pat No. 5,316,057 to Hasselmann describes a vapor recovery system tester. This invention comprises an external ring-like apparatus adapted to fit around and seal to a fuel dispensing spout having vapor recovery apertures. The ring-like apparatus, in turn has a tube connecting it to a air volume measuring instrument which measures the volume of air recovered via the vapor apertures. The recovered volume is then compared to the volume of fuel dispensed to yield an indication of vapor recovery efficiency. Hasselmann is an external device not an internal device. It appears to be directed solely at determining V/L ratios (volume of vapors recovered to the volume of fuel dispensed).
U.S. Pat. No. 5,220,822 to Tuma describes a method for testing vapor recovery lines. Tuma describes a testing method for determining both the integrity and blockage of a vapor recovery system. Tuma requires modifying the vapor recovery unit for vacuum testing. System integrity is tested by drawing a vacuum into the unit to a predetermined level then monitoring it for decay over time in order to determine whether and how severely the system is leaking. System blockage is tested by continuously drawing a vacuum into the unit while the lines are disconnected from the dispensing station at the point most closest to the station. Flow of fluid induced by the vacuum is measured and compared to desired flow rates in order to determine the extent the line is blocked, if at all.
U.S. Pat. No. 4,392,870 to Chieffo et al. describes a vapor recovery unit performance test analyzer and method for use specifically in systems utilizing first and second parallel charcoal beds acting as adsorbing units. In such charcoal bed systems one bed acts to adsorb hydrocarbon vapors while the other is regenerated by vacuum . Once a certain level of adsorption is reached the beds must be switched so that the regenerated bed is now the adsorbing bed and vice-versa. Chieffo et al. describes an electronic monitoring means for both beds utilizing temperature sensors, flowmeters, flow amplifiers, and an electronic unit for obtaining and processing sensed data representing the total hydrocarbon flow of the system. Chieffo et al. appears limited to the parallel charcoal bed configuration described above.
EPO Publication No. EP 0 653 376 A1 to Finlayson describes a vapor recovery system for fuel dispensers. Finlayson is couched in terms of an improved vapor recovery system rather than a tester of vapor recovery systems. It discloses a controller which receives from various sensors signals representative of the fuel vapor/air ratio immediately outside the tank, inside the tank, and/or inside the vapor recovery conduit, and/or the pressure relative to atmosphere inside the tank and/or of the rate of flow of liquid being dispensed. Based on these input signals, the controller operates the vacuum pump at an optimal rate to collect fuel vapor displaced from the tank. Finlayson permits the sensors to be located on the dispensing apparatus itself thereby obviating the need for special sensors and connections in or on the receptacle tank.
U.S. Pat No. 5,450,883 to Payne et al. and U.S. Pat. No. 5,040,577 to Pope, issued to the assignee of the present invention, disclose systems and methods for testing for error conditions in a fuel vapor recover illustrating the general state of the art.
None of the aforementioned references teaches an all encompassing internal diagnostic monitoring and testing system like that of the present invention.